Conventionally, there is known an electric power tool in which an adapter capable of mounting a battery pack having a different rated voltage is provided between a tool body and the battery pack. In an electric power tool described in, e.g., Japanese Patent Application Publication No. 2012-35349, an adapter is provided with a converter circuit. Even when a battery pack having a different rated voltage is used, the electric power supplied to the tool body is adjusted by controlling the electric power (voltage) supplied from the battery pack (power source), that is by performing a step-up or step-down operation with the converter circuit.
In the electric power tool which employs the adapter provided with the converter circuit, there is a need to increase (step up) the battery pack voltage so as to become a rated voltage. When the step-up operation is continuously performed in a state that a work load remains high, there may occur over-current. Possibly, the battery pack may be heated and may be out of order. In view of this, when the over-current or over-discharge is likely to occur, it is considered to cut off the electric power supplied to a load (a motor in case of the electric power tool), thereby stopping the operation of the load. However, such stoppage of the operation of the load may worsen the workability of a user who makes use of the electric power tool.
This holds true in an electric power tool in which a converter circuit as a component of an adapter is provided in a tool body, i.e., an electric power tool having a built-in adapter.